Empirical work has grown in importance in law and economics. This growth coincides with improvements in research designs in empirical microeconomics more generally. In this essay, we provide a stylized discussion of some trends over the last two or three decades, linking the credibility revolution in empirical micro to the ascendancy of empirical work in law and economics. We then provide some methodological observations about a number of commonly used approaches to estimating policy effects. The literature on the economics of crime and criminal procedure illustrates the ways in which many of these techniques have been used successfully. Other fields, including corporate law and economics and the law and economics of civil procedure, have l...